Rack for multichannel pipette cones

ABSTRACT

A rack for pipette cones (in particular multichannel cones) includes orifices in a line forming at least one row along at least an alignment direction and a support surface adapted to support cones housed in the orifices. The rack provides for simultaneous access to at least some of the cones in the row. The support surface has a generally convex transverse outline along the alignment direction.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rack for pipette cones, in particularfor multichannel pipettes.

2. Background of the Invention

Racks presenting a plane support surface in which orifices are providedin a rectangular matrix are known, e.g. from document U.S. Pat. No.3,494,210. A rack of that type can receive cones in the orifices, witheach cone having, for example, a shoulder suitable for bearing on thesupport face. The rack enables a plurality of cones to be fixed to therow of endpieces of a multichannel pipette. Since the spacing betweenthe endpieces corresponds to that of the cones received in the rack, thepipette is placed in such a manner that all of its endpieces penetrateinto respective cones in a row of orifices in the rack. The user thenpresses the pipette against the rack so that the cones are retained onthe endpieces by friction. Thereafter the user moves the pipette away,together with the cones retained on the endpieces. Nevertheless, thattechnique generally does not give satisfaction. When the user pressesthe pipette against the rack, the rack sags in the middle of the row ofcone-receiving orifices. As a result, either the user does not presshard enough so when the pipette is moved away some endpieces are notcarrying cones, in particular endpieces in the middle of the row, orelse the user presses hard and as a result even if there is one cone oneach endpiece, it will subsequently be necessary to pull hard in orderto separate the cones from the endpieces, particularly for endpieces atthe ends of the row.

In addition, the cones, the rack, and the endpieces naturally havegeometrical defects, limited to some extent by manufacturing tolerances.Unfortunately, that gives rise to difficulties when the defects arecumulative in one direction for one endpiece and its associated cone,and in an other direction for another endpiece and its associated cone.This happens for a pipette that possesses a first endpiece whose outsidewidth corresponds to the maximum tolerance and that receives a firstcone whose inside diameter corresponds to the minimum tolerance, and asecond endpiece of the opposite configuration, i.e. of outside widthcorresponding to a minimum tolerance receiving a second cone whoseinside diameter corresponds to the maximum tolerance. Under suchconditions, with the above-mentioned rack, and even when no significantsagging occurs, the first cone will be mounted tightly on the firstendpiece well before the second cone is securely mounted on the secondendpiece. Since the mutually-contacting faces of the cones and theendpieces are conical, that means that the friction zones between thecones and the endpieces on the first and second endpieces are atdifferent heights. This can be made worse by geometrical faults relatingto contact between cones and the support surface. Under such conditions,the greater the geometrical defects in the cones, the endpieces, and therack, the more difficult it becomes to put cones effectively on all ofthe endpieces of a given pipette.

SUMMARY OF THE INVENTION

An object of the invention is to mitigate those drawbacks and to providea rack that makes it possible to fix cones effectively on all of theendpieces of a pipette while requiring only moderate force from theuser.

To achieve this object, the invention provides a rack for pipette cones,in particular for a multichannel pipette, the rack having alignedorifices forming at least one row in at least one alignment direction,and a support face adapted to support cones received in the orifices,the rack making the cones of the row accessible simultaneously, thesupport face having a transverse profile in the alignment direction thatis generally convex in shape.

Thus, the convex shape prevents a concave sag appearing while the conesare being fixed on the endpieces. This ensures that cones are fixedproperly on all of the endpieces of the pipette, and in particular onthe endpieces in the middle of the row. This fixing can be obtained withthe user exerting moderate force only. Thereafter, the force that needsto be supplied to separate the cones from the endpieces is likewisemoderate. In addition, the rack of the invention avoids the need tomanufacture the rack, the endpieces, and the cones to comply with verytight dimensional tolerances. Furthermore, it is not necessary toprovide the rack with reinforcing ribs. The rack can thus bemanufactured, in particular by molding, in a manner that is fast and oflow cost. Also, the rack makes it possible to load each cone on thecorresponding endpiece easily and without excessive tightening, withoutbeing troubled by any geometrical and dimensional defects of the cones,the endpieces, and the rack. To achieve this, it is sufficient, forexample, to use the method of the invention for fixing cones toendpieces by tilting, in the manner described below.

The shape need not be “convex” within the strict meaning of the word,for example it can be convex overall while being concave locally. Forexample, the profile could be M-shaped or camel-humped. Thus, theprofile may present at least one upwardly-projecting zone. The profilecan have at least one middle zone, preferably in its center, which ishigher than the two ends of the profile. In some cases, the shape can bestrictly convex.

Advantageously, the orifices are aligned in two non-mutual parallelalignment directions, the support face having transverse profiles inboth alignment directions that are convex in shape.

Thus, depending on the number of endpieces on the pipette, the rack canbe used with a row of orifices in one or other of the two alignmentdirections, while obtaining the same above-mentioned advantages.

Advantageously, the orifices are aligned so as to form at least two rowsin two respective non-mutually parallel alignment directions, the rack.making the cones in each row accessible simultaneously.

Advantageously, the profile or at least one of the profiles, is roundedin shape.

Advantageously, the profile, or at least one of the profiles, is in theform of a circular arc.

This shape is particularly effective for providing a good distributionof forces on the endpieces for fixing each cone by friction.

Advantageously, the support face is spherical in shape.

Advantageously, the profile, or at least one of the profiles, istriangular in shape.

Advantageously, the rack is constituted by a plurality of portions thatare substantially unmovable relative to one another.

Advantageously, the rack is made as a single piece.

Advantageously, the rack has a support wall defining the support face,and support means connected directly to the support wall and suitablefor supporting it by resting on a base.

Advantageously, the general shape of the rack is that of a rectangularparallelepiped.

The invention also provides a method of fixing cones on the endpieces ofa multichannel pipette in which, starting with a pipette having at leastfirst and second endpieces and with a rack of the invention receiving atleast first and second cones in its orifices, the method comprises thefollowing steps:

placing the pipette relative to the rack in such a manner that theprofile lies in the same plane as the axes of the endpieces, the firstendpiece penetrating into the first cone so as to hold the first cone onthe first endpiece, and the second endpiece extending in register withand at a distance from the second cone; and

tilting the pipette while keeping the profile in the same plane as theaxes of the endpieces so that the first cone held on the first endpiecemoves to a distance from the support face and so that the secondendpiece penetrate into the second cone so as to hold the second cone onthe second endpiece.

This method makes it possible to benefit to a very large extent from theadvantages of the rack of the invention. Contrary to the known method inwhich the pipette is pressed against the rack so as to fix conessimultaneously on all of the endpieces, the method of the inventionmakes it possible to fix cones successively on the endpieces,endpiece-after-endpiece along the row of cones; The user can thus supplyvery moderate force which is nevertheless sufficient to put each coneindividually into place while simultaneously ensuring that the cone isvery well retained by friction on the endpiece.

The invention also provides a method of fixing cones on the endpieces ofa multichannel pipette in which, starting from a pipette having at leasttwo endpieces and a rack of the invention receiving at least two conesin its orifices, the method comprises the steps of:

placing the pipette relative to the rack in such a manner that theprofile lies in the same plane as the axes of the endpieces, theendpieces penetrating into the respective cones; and

urging the pipette towards the rack parallel to the axes of theendpieces so as to retain the cones simultaneously on the respectiveendpieces.

Thus, in this case, the force provided by the user deforms the supportface elastically by flattening its convex shape so as to fix all of thecones effectively to the endpieces.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the invention will appearfurther on reading the following description of a preferred embodimentgiven by way of non-limiting example. In the accompanying drawings:

FIG. 1 is a plan view of a rack constituting a preferred embodiment ofthe invention;

FIGS. 2 and 3 are cross-section views of the FIG. 1 rack respectively onlines II—II and III—III; and

FIGS. 4 and 5 are two fragmentary diagrammatic views of the racktogether with a pipette showing how the method of the invention isimplemented.

FIG. 6 is a cross sectional view of an alternate shape for the supportsurface of the rack of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to FIGS. 1 to 3, the rack 2 comprises a support 4 ofgenerally plane shape, being rectangular in plan, and having a bottomface 6 and a top face 8. The rack has four legs 10 secured to thesupport 4 projecting from its bottom face 6 from the four corners of therectangle, and suitable for supporting the rack on a horizontal plane.

The support 4 has orifices 12 passing through the thickness of thesupport from its top face 8 to its bottom face 6. The orifices 12 aredisposed in a rectangular matrix and are thus aligned in a plurality ofrows in two alignment directions, namely a longitudinal direction 11 anda lateral direction 13, with these two directions being mutuallyperpendicular in this case. Specifically, the matrix has eight orifices12 per row in the width direction and twelve orifices 12 per row in thelength direction. Each orifice 12 comprises a narrow top segmentcontiguous with the top face 8 and a broad bottom segment following thenarrow segment and contiguous with the bottom face 6.

In this case, the bottom face 6 of the rack is plane. Its top face 8 isspherical in shape, with the geometrical center of the sphere being onthe leg side of the support 4. Thus, with reference to FIG. 2, the topface 8 has a transverse profile in the longitudinal direction 11 that isconvex in shape along each longitudinal row of orifices 12. The shape ofthe profile is rounded in the form of a bulging circular arc presentinga small hump 14. Similarly, the transverse profile of the face 8 in thelateral direction 12 is of similar shape for each lateral row oforifices 12 having a hump 16, as shown in FIG. 3. By way of example, theradius of the sphere can be equal to 1 meter (m), the diameter of eachorifice 12 in the top face 4 can be about 5 mm, and the minimum distancebetween two orifices 12 in each row can be about 4 mm. The humps 14 and16 can be about 1 mm to 2 mm in the center of the support. The supporthas an axis of symmetry that is vertical and that passes through thecenter of the rectangle.

The rack 2 is adapted to support cones 18 for the endpieces of apipette, the cones being received in respective orifices 12. The cones18 are so called because of their generally conical shape, and above allbecause of the conical shape of their narrow ends. However they are notexactly conical in shape. In particular, each of them has a circularshoulder on its outside face that is wider than the narrow top segmentof each orifice 12. Thus, a cone 18 received in an orifice 12 bears viaits shoulder against the top face 8 of the support and rests undergravity on said face. The legs 10 are organized in such a manner thatwhen they are placed on a support plane, the narrow ends of the cones 18beneath the bottom face 6 lie at a distance from the support plane.

The cones 18 are adapted to be fixed to endpieces 20 of a multichannelpipette 22 as shown diagrammatically in FIGS. 4 and 5. By way ofexample, such a pipette 22 has eight endpieces 20 having mutuallyparallel axes and lying in a common plane, with the endpieces beingdisposed in a row so that their free ends are in alignment. To clarifythe drawing, a pipette 22 is shown in FIGS. 4 and 5 that has only fourendpieces 20, with the rack of FIGS. 1 to 3 nevertheless being welladapted to a pipette having eight or twelve endpieces, for example.Similarly, to clarify the drawings, the radius of the sphere of the topface 8 is reduced in FIGS. 4 and 5.

The cones 18 are adapted to be held by friction on the free ends ofrespective endpieces 20 so that liquid can then be sucked up from withinthe cones and then expelled by means of the pipette.

To fix the cones 18 on the endpieces 20, it is possible to use themethod of the invention as shown in FIGS. 4 and 5. By way of example, itis assumed that a pipette 22 is being used that has eight endpieces 20(of which only four are shown).

It is assumed that one of the lateral rows of eight orifices 12 in therack has received cones 18. The pipette 22 is placed relative to therack in such a manner that the first endpiece 20 situated at one end ofthe row penetrates far enough into the first cone 18 situated at the endof the row of cones to enable said cone to be held by friction on theendpiece. In addition, all of the other endpieces 20 extend in registerwith respective other cones 18, and possibly penetrate partiallytherein. The last endpiece 20 at the other end of the row of endpiecesis at a distance from the corresponding cone 18. The orifices 12 and theendpieces 20 have effective axes 25 and 23. The profile of the face 8and the axes 23 and 25 lie in a common vertical plane parallel to thelateral direction 13.

The pipette 22 is then tilted as represented by arrow 24 about ahorizontal axis perpendicular to the plane of FIGS. 4 and 5 andperpendicular to the plane common to the axes of the cones and the axesof the endpieces. During this tilting, the profile of the face 8, theaxes 25 of the orifices 12, and the axes 23 of the endpieces 20 allremain in the same plane. The titling is performed in such a manner thatthe first cone 18 is progressively extracted from its orifice 12 in therack while the last endpiece 20 moves towards its cone 18 so as topenetrate therein and retain it by friction. During this movement, allof the intermediate endpieces 20 of the row penetrate successive intothe respective cones 18 and retain them by friction so as to extractthem from the corresponding orifices 12. At the end of this tiltingmovement, as shown in FIG. 5, all of the cones 18 are held by frictionon the endpieces 20 and only the last cone 18 of the row of cones andassociated with the last endpiece 20 of the row of endpieces is stillretained in the original manner in its orifice 12. It then suffices tomove the pipette 22 away from the rack 2, parallel to the axes of itsendpieces, along arrow 26 in FIG. 5. Because each endpiece 20 isinserted into the associated cone 18 and is fixed thereto by frictionindividually and in succession, the user need supply only a moderateamount of force for the purpose of fixing the cones.

Because of the convex shape in the longitudinal direction 11, the rack 2can also be used in the same manner for fixing cones 18 to endpieces inthe longitudinal direction 11 of the rack, for example if the pipette 22has nine to twelve endpieces, with this being done by using any one ofthe longitudinal rows of orifices 12.

Alternatively, it is possible to fix the cones 18 to the endpieces 20 insimultaneous manner, i.e. by inserting all of the endpieces 20 of therow of endpieces at the same time into the associated cones 18 of therow of cones, and exerting a single vertical force downwards on thepipette 22 so as to cause all of the cones to be held simultaneously onthe pipette. Advantage is then taken of the ability of the top face 8 todeform elastically.

Naturally, numerous modifications can be made to the invention withoutgoing beyond the ambit thereof.

The top face 8 of the support can have a transverse profile that isconvex in a single direction only, in which case the cones 18 need to befixed to the endpieces 20 in rows that are parallel to said direction.Thus, the top face 8 could be cylindrical. The profile could be roundedwithout being a circular arc.

As is illustrated in FIG. 6, the profiles could be triangular, in theform of upside-down V-shapes, with the top face 8 then having the shapeof the tip of a diamond, for example.

What is claimed and desired to be secured by Letters Patent of theUnited States is:
 1. A rack for pipette cones, the rack having alignedorifices forming at least one row in at least one alignment direction,and a support face adapted to support the cones received in theorifices, the rack making the cones of the cones row accessiblesimultaneously, and being characterized in that the support face has atransverse profile in the at least one row of the at least one alignmentdirection that is generally convex in shape.
 2. A rack according toclaim 1, characterized in that the orifices are aligned so as to form atleast two rows in two nonparallel alignment directions, the rack makingthe cones in each row accessible simultaneously.
 3. A rack according toclaim 1, wherein the orifices are aligned in two nonparallel alignmentdirections, the support face having transverse profiles in both saidnonparallel alignment directions that are convex in shape andcharacterized in that at least one of the profiles is in the form of aportion of an arc of a circle.
 4. A rack according to claim 1,characterized in that the support face is in the shape of a segment of asphere.
 5. A rack according to claim 1, wherein the orifices are alignedin two nonparallel alignment directions, the support face havingtransverse profiles in both said nonparallel alignment directions thatare convex in shape and characterized in that at least one of theprofiles is triangular in shape.
 6. A rack according to claim 1,characterized in that the rack is constituted by a plurality of portionsthat are substantially unmovable relative to one another.
 7. A rackaccording to claim 1, characterized in that the rack is made as a singlepiece.
 8. A rack according to claim 1, characterized in that the rackhas a support wall defining the support face, and support meansconnected directly to the support wall and suitable for supporting it byresting on a base.
 9. A rack according to claim 1, characterized in thatthe general shape of the rack is that of a rectangular parallelepiped.10. A method of fixing cones on the endpieces of a multichannel pipette,the method being characterized in that, starting from a pipette havingat least first and second endpieces and a rack for receiving at leastfirst and second cones in its orifices, said rack having alignedorifices forming at least one row in at least one alignment direction,and a support face adapted to support the cones received in theorifices, the rack making the cones of the cones row accessiblesimultaneously, and being characterized in that the support face has atransverse profile in the at least one alignment direction that isgenerally convex in shape, the method comprises the steps of: placingthe pipette relative to the rack in such a manner that the profiles liesin a same plane as axes of the endpieces, the first endpiece penetratinginto the first cone so as to hold the first cone on the first endpiece,and the second endpiece extending in register with and at a distancefrom the second cone; and tilting the pipette while keeping the profilein the same plane as the axes of the endpieces so that the first coneheld on the first endpiece moves to a distance from the support face andso that the second endpiece penetrate into the second cone so as to holdthe second cone on the second endpiece.
 11. A rack for pipette cones,the rack having aligned orifices forming at least one row in at leastone alignment direction, and a support face adapted to support the conesreceived in the orifices, the rack making the cones of the cones rowaccessible simultaneously, and being characterized in that the supportface has a transverse profile in the at least one alignment directionthat is generally convex in shape, and being further characterized inthat the orifices are aligned in two nonparallel alignment directions,the support face having transverse profiles in both said nonparallelalignment directions that are convex in shape.